feat: admin Text Gen tool — chapter names + book description via CF Workers AI

Adds backend handlers and SvelteKit UI for an admin text generation tool.
The tool lets admins propose and apply AI-generated chapter titles and book
descriptions using Cloudflare Workers AI (12 LLM models, model selector shared
across both tabs).

backend/cmd/backend/main.go

@@ -133,6 +133,15 @@ func run() error {
 		log.Info("CFAI_ACCOUNT_ID/CFAI_API_TOKEN not set — image generation unavailable")
 	}
 
+	// ── Cloudflare Workers AI Text Generation ─────────────────────────────────
+	var textGenClient cfai.TextGenClient
+	if cfg.CFAI.AccountID != "" && cfg.CFAI.APIToken != "" {
+		textGenClient = cfai.NewTextGen(cfg.CFAI.AccountID, cfg.CFAI.APIToken)
+		log.Info("cloudflare AI text generation enabled")
+	} else {
+		log.Info("CFAI_ACCOUNT_ID/CFAI_API_TOKEN not set — text generation unavailable")
+	}
+
 	// ── Meilisearch (search reads only; indexing is the runner's job) ────────
 	var searchIndex meili.Client
 	if cfg.Meilisearch.URL != "" {
@@ -184,6 +193,8 @@ func run() error {
 			PocketTTS:        pocketTTSClient,
 			CFAI:             cfaiClient,
 			ImageGen:         imageGenClient,
+			TextGen:          textGenClient,
+			BookWriter:       store,
 			Log:              log,
 		},
 	)